Decompression Sickness

Description

A disease process resulting from escape of absorbed gas bubbles (commonly nitrogen) out of solution into body fluids and tissues, affecting multiple organ systems

Background

• Henry’s law:
  • Amount of gas that will dissolve in a solution at a given temperature is directly proportional to partial pressure of that gas in the atmosphere above the solution
  • Increases in partial pressure result in larger amount of gas dissolved in tissue
  • Decreases in partial pressure result in gas coming out of solution and producing bubbles

Etiology

Mechanism:

• Pathophysiology:
  • Increased ambient pressure during diving increases partial pressure of inhaled gases (typically nitrogen, common component of diver’s gas)
  • Gases accumulate in tissues in solution
  • As ambient pressure decreases (ascending in water), gas comes out of solution and back into a gaseous state
  • Decompression sickness (DCS) results when rapid pressure changes do not allow for gradual removal of excess nitrogen or inhaled gas
  • Supersaturation of tissues when gases not eliminated rapidly enough and bubble formation results
• Bubbles incite inflammatory and coagulation responses:
  • Increased vessel permeability, hemoconcentration, edema, endothelial dysfunction, clot formation
  • Resulting disruption of blood flow or lymphatic drainage can to ischemia, infarction, or lymphedema
  • Clinical effects determined by bubble location and extent
• Risk factors for DCS:
  • Dive factors:
    • Greater depth
    • Prolonged time at depth
    • Multiple dives in a day
    • Rapid ascent
    • Cold water
  • Human factors:
    • Patent foramen ovale (PFO)
    • Obesity
    • Concurrent illness
    • Pulmonary disease
    • Dehydration
    • Smoking history
    • Alcohol use prior to dives
  • Proper use of dive tables, timers, and computers does not completely eliminate risk for DCS, though can help mitigate it
• 50% of patients develop symptoms in 1 hr, 90% develop symptoms within 6 hr, but can present up to 36 hr postdive
• Airplane flight within 12–24 hr following diving can precipitate DCS due to lower cabin pressure

Epidemiology

• Due to improvements in diving tech and safety protocols, DCS is increasingly rare
  • Recreational divers
    • 3 per 10,000 dives
  • Higher for commercial divers